Hello JAMBITES, StudiHUB will be giving a brief ‘Summary on Biology’. We’ll be summarizing Biology, defining major terms in the subject, and listing a few things that have probably been forgotten. Most of the definitions were obtained from ‘ESSENTIAL BIOLOGY’, so read up and read well.

Epic summary of Biology by StudiHUB group.
Let’s summarize biology


Living things are divided into 5 kingdoms;

  1. Monera- Schizophyta and Cyanophyta
  2. Protista- Euglenophyta, Protozoa, Chrysophyta, and Pyrrophyta
  3. Fungi
  4. Plantae- Thallophyta (green, brown, red algae), Bryophyta (liverworts and mosses), Tracheophyta (vascular plants). Tracheophyta is divided into Pteridophyta and Spermatophyta (Angiosperms and Gymnosperms)
  5. Animalia- Porifera (sponges), Coelenterata (hydra, jellyfish), Platyhelminthes (flatworms), Nematoda (roundworms), Annelida (earthworm), Mollusca (octopus, snail, mussel), Arthropoda (crustacea, insecta, arachnida, myriapoda), Echinodermata (starfish, sea urchin), and Chordata (vertebrata- pisces, amphibia, reptilia, aves, mammalia)

A virus is a microscopic organism made up of coiled strand of nucleic acid (i.e. Ribonuclei Acid (RNA) or Deoxyribonuclei Acid (DNA)) enclosed within a protein coat. It doesn’t have a cell structure, and can act as a living and non-living thing.

Cell Components/Organelles and Their Functions

1 Nucleus Controls all life activities of the cell Stores hereditary information as it contains DNA inside chromosomes
2 Chromosome Contains the DNA which stores genetic trait
3 Mitochondria The power-house of the cell Site of respiration or where energy is released from simple sugar
4 Vacuole Contains cells sap which act as an osmoregulator by helping to remove excess water in cells
5 Nucleolus Produce the ribosome for protein synthesis
6 Endoplasmic reticulum Aids the transport of materials within the cytoplasm
7 Golgi Bodies Function in synthesis, packaging and distribution of materials
8 Chloroplasts Contain chlorophyll which aid photosynthesis in plants
9 Lysosomes Site for respiratory enzymes
10 Ribosomes Responsible for protein synthesis
11 Cell Wall Provides protection, shape, and mechanical support for the cell Allows free passage of nutrients in and out of the cell
12 Cell Membrane Plays a great role in selective absorption of materials Protects the cells
13 Centrioles Important in cell division Serve as a basal body
14 Starch Granules Store starch for the cell

Difference between Plant and Animal Cells

1 Contains chloroplast Absence of chloroplast
2 Rectangular and definite in shape Spherical or no definite shape
3 Rigid cell wall No cell wall
4 Large vacuoles Small vacuoles
5 Nucleus at the edge of cytoplasm Nucleus at the center of the cytoplasm
6 Absence of centriole and centrosomes Presence of centriole and centrosomes

They both contain; Golgi bodies, mitochondria, chromosome, cell membrane, lysosome, cytoplasm, nucleolus, endoplasmic reticulum, and ribosome.

Diffusion is the movement of ions or molecules from a region of higher conc. to a region of lower conc. until they are evenly distributed.

DIFFUSION: Process by which molecules or ions of a substance (gases and liquids) move from a region of high concentration to a region of lower concentration until they are evenly distributed (substances may be liquids, gases, or solid).

OSMOSIS: Flow of water or solvent molecules from a region of dilute or a weaker solution to a region of concentrated or stronger solution through a selectively or differentially permeable membrane (it is a special form of diffusion).

PLASMOLYSIS: The outward movement or flow of water from living cells when they are placed in a hypertonic solution (it is often regarded as the opposite of osmosis). This process involves the withdrawal of water from living cells up to the extent of pulling away the cytoplasm from the cell membrane or cell wall. This will result in the shrinkage of the cytoplasm and collapse of the cell.

HAEMOLYSIS: Process by which red blood cells or corpuscles become split or burst as a result of too much water passing into it. This occurs when the red blood cell is place in a hypotonic solution.

TURGIDITY: Condition in which cells absorb plenty of water up to a point where the cell is fully stretched

FLACCIDITY: the condition in which plants lose water to their surroundings faster than they can absorb.


The irreversible or permanent increase in size, dry mass, or weight due to the addition of living protoplasmic materials in organisms.


  1. Cell division
  2. Cell enlargement
  3. Cell differentiation


  1. Mitosis: a cell or nuclear division following the duplication of the chromosomes, whereby each daughter cell or nucleus has exactly the same chromosome content as the parent.

STAGES OF MITOSIS: Interphase, Prophase, Metaphase, Anaphase, and Telophase


  • Promotes cell growth
  • Helps in the replacement or repair of damaged tissues
  • Basis of asexual or vegetative reproduction
  • Produces offspring genetically identical to the parents
  • Helps to maintain the diploid number of the chromosome of the cell
  • Meiosis: this is a two successive cell division with only one duplication of chromosomes. It is a reduction in cell division and the resulting four daughter cells are haploid.

STAGES OF MEIOSIS: 1ST meiotic division (parent cell split into two)

2ND meiotic division (the products then divide again giving a total of 4 daughter cells)


  • Aids the formation of sperms or male gametes in animals
  • Aid the formation of ova (eggs) or female gametes in animals
  • Aids the formation of pollen grains in anthers of flowering plants
  • Aids the formation of ovule in ovary of flowering plants

REPRODUCTION: The ability of living organisms to give rise to new individuals of the same species


  • Asexual reproduction: the type of reproduction in which new organisms are produced from a single parent without the production of gametes
  • Sexual reproduction: this involves the fusion of the male gametes, e.g. sperm cells and the female gametes (ova or egg cell) to form a zygote which later develops into a young offspring.

Asexual reproduction has different types; Binary fission, Budding, Spore formation, Vegetative reproduction.

A ‘SPORANGIOSPHORE’ is an upright hyphae on which numerous spores in the sporangia are borne.

The Human Skeleton

SKELETON: is the bony framework of the body which provides supports, shapes, and protection to the soft tissues and organs in animals.

Forms of skeletal materials: Cuticles, Bones, and Cartilages


  • Hydrostatic skeleton- skeleton possessed by soft-bodied animals
  • Exoskeleton- found outside or external part of the body of some animals
  • Endoskeleton- found inside the body of animals

AXIAL SKELETON: made up of the skull, vertebral column (backbone), the ribs, and sternum (breastbone)

APPENDICULAR SKELETON: limb girdles (pectoral and pelvic girdles) and the limbs (fore limbs and hind limbs)


Ecology is the study of plants and animals in relation to their environment. It is a field of study which deals with the relationship of living organisms with one another and with the environment in which they live.


  1. Forest zone: is made up of vegetation having mainly trees and consists of; Mangrove swamp and Tropical rainforest. Mangrove swamp forest is divided into Salt and Freshwater swamp.
  2. Savanna zone: is made up of mainly grasses and is sub-divided into 3 savanna belts;
    1. Southern guinea savanna
    1. Northern guinea savanna
    1. Sahel savanna


  1. Tropical Rainforest
  2. Savanna
  3. Desert
  4. Shrub
  5. Afro-alpine
  6. Swamp


This is the total number of organizations of the same species of living together in a given area at a particular time.

POPULATION DENSITY: this is the number of individual organisms per unit area or volume of the habitat

Mathematically, Pop. Density = Total Population (population size) / Area of Habitat


  1. Short sightedness (myopia): this is a condition in which parallel light rays from a distant object are brought to a focus in front of the retina. It may be caused by the eyeball being too long or the lens being to convex (too thick).

Correction: By wearing spectacles fitted with concave or diverging lenses

  • Long sightedness (hypermetropia): this is a condition in which parallel light rays from near objects are brought to a focus behind the retina. It may be caused by the eyeball being too short or the lens being too flat.

Correction: By wearing spectacles fitted with suitable convex or converging lenses.

  • Presbyopia: this is the loss (with age) of the elasticity of the lens and ciliary muscles. It leads to the loss of accommodation.

Correction: By wearing bi-focal lenses (a combination of convex and concave lenses)

  • Astigmatism: this is caused as a result of unequal curvature of the cornea or lens. The image blurs because of the different points of focus of the light rays on the retina.

Correction: By using cylindrical lenses.

Accommodation: the ability of the eye to focus (both near and distant) objects on the retina.

Other eye defects are; Color blindness, Night blindness, Cataract, Conjunctivitis.

Dicotyledonous seeds undergo epigeal germination


A seed is a ripened fertilized and developed ovule.

Structure of the Seed; Seed coat/ testa, Hilum, Micropyle, Embryo

Monocotyledonous seed: a seed having only one cotyledon (e.g. rice, wheat, maize)

Dicotyledonous seed: a seed having two cotyledons (e.g. beans, mango)

GERMINATION: The process which involves the gradual development of the embryo of the seed into a seedling or a young plant.

Types of Germination;

  1. Epigeal Germination: this is a germination in which the cotyledons or seed leaves are carried above the soil surface. It is associated with dicotyledonous seeds.
  2. Hypogeal Germination: this is a germination in which the cotyledons remain below the soil surface. It is associated with monocotyledonous seeds.


Genetics is the scientific study of heredity and variation in living things.

HEREDITY: this is the transmission and expression of characters or traits in organisms from parents to offspring.

VARIATION: this is the morphological and physiological differences which occur within a species which could be hereditary or acquired from the environment.

Some Important Terms in Genetics

  1. Genes: genes are hereditary units or basic units of inheritance, located in the chromosomes. They are responsible for the transmission of characters from parents to offspring.
  2. Gametes: gametes are matured sex cells which take part in sexual reproduction.
  3. Phenotype: this is the sum total of all observable features of an organism (physical, physiological, and behavioral traits).
  4. Genotype: this is used to describe the traits or sum total of the genes inherited from both parents.
  5. Dominant character: this is a trait or character that is expressed in an offspring when two individuals with contrasting characters or traits are crossed.
  6. Recessive character: this is the character or trait from one parent which is masked or does not produce the effect in the presence of the dominant character.
  7. Chromosomes: these are rod or thread-like bodies found in the nucleus of a cell. They house the genes.
  8. Allelomorphs: these are pairs of genes on the position of a chromosome that control contrasting characters.
  9. Characters or Traits: these are the inheritable attributes or features possessed by an organism.

Others include; Homozygous, Heterozygous, Filial generation, Hybrid, Hybridization, Locus, Haploid, Diploid, and Mutation.

Gregor Mendel’s Laws of Inheritance

Gregor Mendel (1822 – 1884) was a monk in an Augustinian monastery in Brunn, Austria. He is often regarded as the father of genetics because his work formed the foundation for scientific study of heredity and variation. He worked with the garden pea (Pisum sativum). Gregor used artificial method to cross two different plants, at a time, which differed in one pair of contrasting characters, e.g. tall and short plants. This procedure was called ‘Monohybrid Inheritance’ and it was an example of complete dominance.

MENDEL’S FIRST LAW OF INHERITANCE (law of segregation of genes)

This law states that genes are responsible for the development of the individual and that they are independently transmitted from one generation to another without undergoing any alteration.

MENDEL’S SECOND LAW OF INHERITANCE (law of independent assortment of genes)

This law states that each character behaves as a separate unit and is inherited independently of any other character.

TEST CROSS: this is the crossing of an organism with the homozygous recessive organism.

BACK CROSS: this is the crossing of an organism with the homozygous recessive organisms from the original parental generation.

Tests cross and back cross are used to determine the genotype of organisms showing dominant phenotype.


Incomplete dominance is the ability of two contrasting alleles to interact and produce a heterozygous phenotype different from the two homozygous phenotypes.


Organic evolution: is the sum total of adaptive changes from pre-existing or old form that has taken over a long time, resulting in diversity of forms, structures and functions among organisms.

Types of Variation

  1. Morphological Variation: this refers to the noticeable physical appearance of individuals of the same species. Types of morphological variation in human beings are;
  2. Height
  3. Shape of body parts, e.g. moth, nose
  4. Fingerprint
  5. Size of body parts such as head, eyes
  6. Color of body parts e.g. eyes, hair, skin
  7. Weight
  8. Physiological Variation: this relates to the differences in the ways individuals of the same species behave or react to conditions in their environment i.e. functioning of the body.
  9. Behavior
  10. Ability to roll the tongue
  11. Ability to close one eye and keep the other open (winking)
  12. Ability to move the ears without moving the head
  13. Ability to taste PTC
  14. Difference in blood group
  15. Fingerprints

Variation is caused by two factors;

  1. Genetic differences
  2. Influence of the environment

That would be all; we implore you to visit www.studihub.com.ng to watch videos on various subjects and an extensive explanation of biology.